High idle problem

crackedback said

Try disconnecting the throttle limkage.

Make sure none of the throttle linkage parts are binding on your intake. That's been a 40yo issue. Check them all especially the secondary, pass side.

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Exellent suggestion.
Make sure they are not binding against each other also, and make sure your fast idle screw is backed off.
(You know, the one undeneath the linkage facing up.)
I have the same carb you do and with everything backed down all the way I can barely get it down to 900 R's when warmed up.
It seems to be kind of a balance between timing advance amount and idle mixture.